Backfire trap



Oct. 7, 1952 A. CARNAHAN BACKFIRE TRAP Filed Jan. 10, 1950 Patented Oct. 7, 19 52 UNITED STATES PATENT'OFFICE w "2,818,144 I I LBAQKFIBE TRAP, Grson A. Carnahan, Syracuse, N. Y. Applicafitn Jan'iiary io, 1950, serial No. 137,800

This invention is directed to back Afire traps for internal combustion engines; and relates more particularly to improved flame l`arresting elements, mountings therefor, and to novel methods for constructing and assembling said traps and the components thereof.

Back fire traps, such, for example, as are disclosed in my Letters Patents Nos. 1,9%,0-14 and 1,946,015 dated February 6, 1934, comprise in brief a conduit or housing, a flame arresting element which serves to absorb'heat and thus reduce the temperature of the gases passing therethrough below the kindling temperature, and mounting means for securingthe flame arresting element in the path of the gases passing through said housing. i

The flame arresting elements which are usually formed by winding a strip of thin metal provided with transverse corrugations or other members projecting beyond thesurface thereof and a spacer strip of thin material, have heretofore been secured in the path 'of the gases'by the use of radially extending' reinforcing bar's soldered to the core and to the convolutions of the element. Even by exercising a maximum of care during manufacture, it was found that solder became lodged in many of the openings of the fiame arrestor element, and this 'additional' solder together with the reinforcing members presented an obstruction to the fiow of gas therethrough. Further, the fiame arresting elements have heretofore been mounted in the path of the gas flow through the conduits lor `housings by the use of frames, plates, and screws 'whichengine. i

It is, therefore, an object of this invention 'to' provide an improved back fire trap wherein the convolutions of the flame arresting element are secured by the use of reinforcing members which pass in a radial direction through the'convolutions with a friction fit and are anchored in the core and thus do not necessitate the use of solder to maintainthem in position. o l

Another object of this invention is to'maintain the core of the flame arresting element in position by the use of a plurality of reinforcing bars which pass therethrough thus eliminating the soldering operation. i j

Another object of the invention is to'provide an improved back fire trap wherein the kpassages through the name arresting element offer low i elaim. (ci. 48-192) resistance to the flow of air since they are not impeded by solder or. other foreign material.

Another object of the invention is to provide an improved one piece housing for securing the flame arresting element in position in the path of the moving gases which pass through the back fire trap without the use of frames, plates, and screws, which housing also serves to maintain the reinforcing bars of the fiame arresting element against dislodgement in a radial direction. i

A still further'object of the invention is to provide an improved back fire trap which is formed with relatively few parts that may be easily and quickly assembled.

The invention also resides in certain novel structural characteristics which facilitates the carrying out of the foregoing objects and which contribute both to the efficiency of the back fire trap and to its ruggedness of constructionv as well as to the dependability of its operation.

Other objects and advantages of the invention will become apparent from the following detailed description' taken in connection with the accompanying drawings, in which:

Eigure 1 is a side view partly in section of the improved back fire trap; i

Figure 2 ,is a front elevation partly in section of the improved back fire trap shown in Figure 1;

Figure 3 is avsectional view of the housing of the back fire trap; I

Figure 4 is a side 'elevation partly in section of the' core which forms a part of the flame arresting element; and

Figure 5 is a plan view of the core structure shown in Figure 4.

While the invention is susceptible of various modifications and alternative constructions and methods, I have shown in the drawings and will herein describe indetail the preferred embodiment. It is to be understood, however, that I do not intend to limit the invention to such disclosure for I aim to cover all modifications and alternative constructions falling within the spirit and scope of the invention as defined in the appended claims.

The improved .back fire trap comprses a housingor conduit 3 and a flame arresting element 12 transvers'ely` positioned across one end of the housing in the path of the gases flowing therethrough, as is best shown in Figures 1 and 2. The housing 3 comprises a hollow tubular member preferably formed of metal, which is provided with an outlet opening |3 and an inlet positioned between the end openings thereof v identified by reference numeral |5.

The inlet end or opening [4 of housing 3 is formed with a fiattened annular rim member IB which joins the flared section |5 by an abruptly turned section positioned in the wall of .the housing. The abruptly turned section forms an annular ledge 9 on the interior wall which is located a spaced distance from the terminal edge of the housing. v

The fiame arresting element |2 which is' subsequently secured interorly of the attened rim member IG is formed by winding a corrugated strip of thin metal 2 and a spacer strip I formed of thin fiat material, such as metal Vor heat resistant plastic about a core or center pin 4. The strips are wound in superposed relation with the spacer strips in contact with a face of the cor-l rugated strip. In using the term corrugated strip" I mean to include strip material which is transversely corrugated and also material provided with projections or other means for spacing apart the adjacent turns 'or convolutions of the strip in order to form passages for the fiow i of gas through the flamearresting element. The core or center pin 4 is preferably formecl with a cylindrical shaped body portion which is provided with an annularly fianged head at one end thereof. The portion of. the core upon which the corrugated strip and spacer strip are wound has a length substantially equal to the width of the strips as is shown in Figure 1.

A plurality of spiral turns of the combined corrugated strip and spacer strip. are applied to core 4 to form the fiame arresting element |2., and as is best shown in Figure 2 the resulting structure is provided with a large. number of air passages in each of the convolutions between the corrugated member and the spacer strips. A rsunicient number of turnsare wound on the core to provide the fiame arresting element with a diameter so that it willfit snugly Within the flattened rim member It of housing 3.

After the winding operation,V the fla-me arresting element is then provided, by drilling' or the like, with a plurality of passages l'i and |8 'which extend between the peripheral surfaces of the' fiame arresting element and pass through the core M. Thus, the passages have a length substantially equal to the diameter of the fiame arresting element. As is best shown in Figure 1, the passages are offset laterally along the axis of core so that they exist independently o f each other. The passages are also 'angularlydisplaced from one another in a. plane transverse to the axis of the core. I'

Holes indicated by reference numerals 'I and 8 are provided in core 4, and these holes are positioned in alignment with passages ll and IB. g As indicated in Figures 4 and 5, the holes extend through the core memberll and eachof the holes is offset laterally a spaceddistance along the axis of the core member. and are located in angular relation to each other.

After the corrugated strip and spacer strip have been wound on the core and the convolutions of the strip and the core provided with passages ll' and IB as heretofore set forth, reinforcing members 5 and 6 are inserted in the passages in order to hold the convolutions of the strip members in place and also the core member is position relative to the convolutions, As shown in Figures 1 and 2, reinforcing members 5 and 6 comprise bars having a circular cross section, although it is within the scope of this invention to use rein- ,forcing members having other cross sectional configurations. Reinforcing members 5 and 6 have a length which Will span between the peripheral edges of the fiame arresting element and are selected of a size to fill passages ll and [8 as well as holes 'I and 8 and to have a frictional fit with the material of the convolutions and core. It will be apparent that the reinforeing bars 5 and 6 serve to maintain the convolutions and corerin position and additional parts, terials, and Operations are unnecessary to provide a fiame arresting element which is rigid in construction and in which the tran-svcrse air passages are substantially unobstructed.

This invention contemplates the use of rolnforcing members 5 and 5 which have a length substantially equal to the radius of the fiame arresting element, and further it is within the scope of this invention to employ any selected number of reinforcing members, each of which is angularly displacecl in a plane transverse to the axis of the fiame arresting element.

After the fiame arresting element 2 has been formed in the aforementioned manner, it is inserted within the inlet opening lt of housing 3 interiorly of annular rim IG, and positioned with the annular edge of the inner face thereof in contact with the ledge 9.

The fiame arresting element (2 is secured in position in housing 3 by bending inwardly over the. edge of the fiame arresting element the metal forming the terminal edge of the housing to provide an inwardly extending annular rim lO which serves securely to lock the assembly. The rim IO may be formed by any conventional metal working operation, such, for example, as spinning, pressing, or peening, whereby the metal of the rim is formed at substantially right angles to the flattened annular rim member HS.

I claim:

A back fire trap for internal combustion engines comprising in combination, a tubular metal housing provided with a ledge positioned on the interior wall thereof a spaced distance from a terminal edge of said housing, a preformed fiame arresting element positioned within said tubular housing in abutment with saidledge comprising a core member formed with a cylindrically shaped body portion, a plurality of convolutions of a transversely corrugated thin metal strip and a spacer strip of thin material positioned in contact with a side thereof spirally wound about the cylindrical body portion of said cylindrical core member, a plurality of passages each extending in a radial direction. in alignment through said core member and con'- volutions of said strips and having a length substantially equal to the diameter of said fiame arresting element, said passages being angularly disposed with respect to one another and oilset a spaced distance along the axis of said core and convolutions, a reinforcing member positioned within each of said passages in frietionei contact with the wall thereof land extending between the peripheral surfaces of said fiame arresting element to maintain said core and strips in the aforesaid pre-formed arrangement, and an annular rim extending inwardly adjacent said terminal edge of the housing and over the edge of said flame arresthg element for maintaining said element in abutment with said ledge.

ORSON A. C'ARNAI-IAN.

REFERENCES CITED The following references are of record in the file of this patent:

Number 6 UNITED STATES PATENTS Name Date Brooks Aug. 21, 1928 Calhoun Nov. 12, 1929 Dobbins Jan. 5, 1932 Carnahan Feb. 6, 1934 Jurs May 13, 1947 

